package com.atguigu;

import org.junit.Test;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Date;
import java.util.Iterator;
import java.util.Scanner;

/**
 * 一、使用 NIO 完成网络通信的三个核心
 *
 * 1. 通道（Channel）：负责连接
 *
 *      java.nio.channels.Channel 接口：
 *          |--SelectableChannel
 *              |--SocketChannek
 *              |--ServerSocketChannel
 *              |--DataGramChannel
 *
 *              |--Pipe.SinkChannel
 *              |--Pipe.SourceChannel
 *
 * 2. 缓冲区（Buffer）：负责数据的存取
 *
 * 3. 选择器（Selector）：是 SelectableChannel 的多路复用器。用于监控 SelectableChannel 的 IO 状况
 *
 * @author lipengyu
 * @date 2019/9/2 9:28
 */
public class TestNonBlockingNIO{

    //客户端
    @Test
    public void client() throws IOException {
        //1. 获取通道
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));

        //2. 切换非阻塞模式
        sChannel.configureBlocking(false);

        //3. 分配指定大小的缓冲区
        ByteBuffer buf = ByteBuffer.allocate(1024);

        //4. 发送数据给服务端
        Scanner scan = new Scanner(System.in);

        while(scan.hasNext()) {
            String str = scan.next();
            buf.put((new Date().toString() + "\n" + str).getBytes());
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }

        //5. 关闭通道
        sChannel.close();
    }

    //服务端
    @Test
    public void server() throws IOException {
        //1. 获取通道
        ServerSocketChannel ssChannel = ServerSocketChannel.open();

        //2. 切换非阻塞模式
        ssChannel.configureBlocking(false);

        //3. 绑定连接
        ssChannel.bind(new InetSocketAddress(9898));

        //4. 获取选择器
        Selector selector = Selector.open();

        //5. 将通道注册到选择器上，并且指定“监听接受事件”
        ssChannel.register(selector, SelectionKey.OP_ACCEPT);

        //6. 轮询式的获取选择器上已经“准备就绪”的时间
        while(selector.select() > 0) {

            //7. 获取当前选择器中所有注册的“选择键（已就绪的监听时间）”
            Iterator<SelectionKey> it = selector.selectedKeys().iterator();

            while (it.hasNext()) {

                //8. 获取准备就绪的是事件
                SelectionKey sk = it.next();

                //9. 判断具体是什么事件准备就绪
                if (sk.isAcceptable()) {

                    //10. 若“接受就绪”，获取客户端连接
                    SocketChannel sChannel = ssChannel.accept();

                    //11. 切换非阻塞模式
                    sChannel.configureBlocking(false);

                    //12. 将该通道注册到选择器上
                    sChannel.register(selector, SelectionKey.OP_READ);
                } else if (sk.isReadable()) {

                    //13. 获取当前选择器上“读就绪”状态的通道
                    SocketChannel sChannel = (SocketChannel) sk.channel();

                    //14. 读取数据
                    ByteBuffer buf = ByteBuffer.allocate(1024);

                    int len = 0;

                    while ((len = sChannel.read(buf)) > 0) {
                        buf.flip();
                        System.out.println(new String(buf.array(), 0, len));
                        buf.clear();
                    }
                }

                //15. 取消选择键 SelectionKey
                it.remove();
            }
        }
    }
}

















